The objectives of the present project are first, to explore further the capacity of the rabbit visual system to re-organize itself following injury, and the factors underlying such process, and second, to continue studies on its normal physiological mechanisms of structural organization. The first five studies examine the degree of plasticity in the visual system. Proline electronmicroscopic-autoradiograph (EM-ARG) studies will be used to study the presence of synaptic terminals of the anomalous uncrossed retinotectal fibers. ARG procedures will be used to determine the arrival time of retinotectal projection, and also the occurrence of crossed cortical projection in rabbits who had unilateral striate cortical lesions at birth. Rabbits with prenatal striate lesions will be tested on visual discrimination learning. Unit recordings will be made on superior colliculus cells in rabbits who had unilateral enucleation at birth and sectioning of collicular commissure. The second group includes studies on the functional classification of colliculus cells responsive to electric shocks to striate cortex, the effect of visual deprivation on the X- and Y- cells in the lateral geniculate nucleus, and the distribution of the projections from the two eyes to the binocular region of the striate cortex.